Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
A typical radio access wireless (RAN) network includes a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. Further, the base stations are then coupled with network infrastructure of the RAN that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the RAN may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the RAN.
In general, a RAN may operate in accordance with a particular radio access technology or “air interface protocol,” with communications from the base stations to UEs defining a downlink or forward link and communications from the UEs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE) or Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), and Global System for Mobile Communications (GSM), among others. Each protocol may define its own procedures initiation of communications, handover between coverage areas, and functions related to air interface communication.
In one particular arrangement, a RAN may provide a UE with connectivity to a packet-switched network, such as the public Internet and/or a private network, and the packet-switched network may in turn provide connectivity with a call server platform that facilitates call connections (generally any real-time communication sessions, such as voice calls, video sessions, or the like) with remote parties. An example of such a call server platform is the Internet Multimedia Subsystem (IMS), which includes one or more call servers (e.g., gateways, controllers, conference bridges, etc.) that function to set up, manage, and carry packet-based call connections between parties.
When a UE is in coverage of a RAN that provides the UE with connectivity to an IMS, the UE may engage signaling, such as Session Initiation Protocol (SIP) signaling, with the IMS to place or receive calls. For instance, to place a call, the UE may transmit via the RAN to an IMS call server a SIP INVITE designating a called party telephone number or address. In response, the IMS call server may then engage in further SIP signaling to set up a call connection with the called party (e.g., via another call server serving the called party) and to set up a call connection with the UE, and the IMS call server may then bridge those call connections together to allow UE to communicate with the called party. Likewise, if the IMS call server receives a request to set up a call from another party to the UE, the IMS call server may similarly engage in SIP signaling with the UE via the RAN to establish a call connection with the UE and may bridge that call connection with a connection to the calling party.
While a UE is engaged in such a call via the RAN, the IMS call server may regularly monitor its call connection with the UE, such as to ensure that communication traffic and/or signaling continues to flow between the UE and the IMS call server. If the IMS call server detects an absence of such communication traffic and/or signaling without receiving a normal call disconnect request (e.g., a normal end-of-call signal resulting from one of the parties hanging up), the IMS call server may responsively take action to tear down the other side of the call. For instance, the IMS call server may responsively transmit a SIP BYE message to a call server serving the other party in order to cause the other call server to tear down its connection with the other party. (Alternatively, if the same IMS call server is serving both the UE and the other party, that IMS call server may process such a tear-down internally.)